Optimization of welding parameters for laser bead-on-plate welding using Taguchi method

This paper presents the results obtained by the optimization of laser bead on plate welding parameters for 3.5 kW cooled slab laser using Taguchi technique. The trials were conducted on two different shielding gases 100% Nitrogen and 50% Nitrogen + 50% Argon. The input process parameters such as beam power, travel speed and focal position are selected suitably in order to obtain the desired output i.e., bead width and depth of penetration. The quality of the weld is evaluated by studying the features of weld bead geometry. Grey relational analysis is applied to optimize the input parameters simultaneously considering multiple output variables. In this investigation the nearest optimal solution which would improve the weld quality was found out. Experimental trial on super austenitic stainless steel has been conducted to validate the optimized parameters. Further, the optimized parameters were evaluated through the microstructural characterization and hardness measurements across the weld zone.     

Sensitivity analysis of submerged arc welding process parameters

Selection of process parameters has great influence on the quality of a welded connection. Mathematical modelling can be utilized in the optimization and control procedure of parameters. Rather than the well-known effects of main process parameters, this study focuses on the sensitivity analysis of parameters and fine tuning requirements of the parameters for optimum weld bead geometry. Changeable process parameters such as welding current, welding voltage and welding speed are used as design variables. The objective function is formed using width, height and penetration of the weld bead. Experimental part of the study is based on three level factorial design of three process parameters. In order to investigate the effects of input (process) parameters on output parameters, which determine the weld bead geometry, a mathematical model is constructed by using multiple curvilinear regression analysis. After carrying out a sensitivity analysis using developed empirical equations, relative effects of input parameters on output parameters are obtained. Effects of all three design parameters on the bead width and bead height show that even small changes in these parameters play an important role in the quality of welding operation. The results also reveal that the penetration is almost non-sensitive to the variations in voltage and speed.     

Sensitivity analysis for process parameters in GMA welding processes using a factorial design method

Generally, the quality of a weld joint is strongly influenced by process parameters during the welding process. In order to achieve high quality welds, mathematical models that can predict the bead geometry and shape to accomplish the desired mechanical properties of the weldment should be developed. This paper focuses on the development of mathematical models for the selection of process parameters and the prediction of bead geometry (bead width, bead height and penetration) in robotic GMA (Gas Metal Arc) welding. Factorial design can be employed as a guide for optimization of process parameters. Three factors were incorporated into the factorial model: arc current, welding voltage and welding speed. A sensitivity analysis has been conducted and compared the relative impact of three process parameters on bead geometry in order to verify the measurement errors on the values of the uncertainty in estimated parameters. The results obtained show that developed mathematical models can be applied to estimate the effectiveness of process parameters for a given bead geometry, and a change of process parameters affects the bead width and bead height more strongly than penetration relatively.     

基于多因素权重法的高压GMAW焊缝成形分析

水下高压干式GMAW焊缝成形难以控制,影响焊接质量,通过多因素权重法对影响高压GMAW焊缝成形的参数进行分析,以确定焊接过程中主要参数与焊缝成形之间的关系. 以高压GMAW焊接正交试验结果作为训练样本,利用BP神经网络建立了焊缝成形预测模型. 将模型预测结果与实际焊接试验结果进行对比,验证了模型的精确度. 以预测模型中的权值为基础,通过Garson算法得出各参数变量对于焊缝成形参数的权重系数,并通过高压干式GMAW试验进行验证. 结果表明,不同焊接参数变化引起的焊缝成形参数变化幅度与相应焊接参数对焊缝成形的影响权重基本对应,所得权重系数对于高压GMAW焊接工程应用具有指导作用.     

Sensitivity model for prediction of bead geometry in underwater wet flux cored arc welding

To investigate influence of welding parameters on weld bead geometry in underwater wet flux cored arc welding (FCAW), orthogonal experiments of underwater wet FCAW were conducted in the hyperbaric chamber at water depth from 0.2 m to 60 m and mathematical models were developed by multiple curvilinear regression method from the experimental data. Sensitivity analysis was then performed to predict the bead geometry and evaluate the influence of welding parameters. The results reveal that water depth has a greater influence on bead geometry than other welding parameters when welding at a water depth less than 10 m. At a water depth deeper than 10 m, a change in travel speed affects the bead geometry more strongly than other welding parameters.     

Effect of heat input on the Fe-based nanostructured weld overlay

In the last few years, several welding consumables have been developed that deposit hard iron-based nanostructured alloy coverings with high resistance to abrasive wear. The erosive and abrasive wear resistances are mainly controlled by the chemical composition and the microstructure. In turn, the microstructure of the deposited metal can show variations with the used welding procedure, particularly in relation to the heat input. The operating parameters that define the heat input (voltage, current and welding speed) affect aspects such as bead geometry (wide, penetration and reinforcement) and dilution with the base material. The purpose of this article is to study the effect of heat input on the geometric characteristics of the bead, the dilution and the microstructural evolution of a nanostructured iron-based alloy deposited by FCAW. Several samples with heat input between 0.5 and 3.5 kJ/mm were welded. A dimensional study was carried out for each welded coupon, the chemical composition was analysed and the microstructure was characterized using optical and electronic scanning microscopy and X-ray diffraction. Microhardness, crystallite size and degree of dilution were also measured. Great influence in these conditions in the process was observed about the geometry of the bead. The dilution varied between 30% and 40%; microhardness of the deposit was found between 800 and 870 HV1, and the size of the crystallite varies between 105 and 130 nm, depending on process variables used. The highest hardnesses and the lowest crystallite sizes were obtained with the lowest heat input, associated with a lower dilution.     

Optimization and Prediction of Angular Distortion and Weldment Characteristics of TIG Square Butt Joints

Autogenous arc welds with minimum upper weld bead depression and lower weld bead bulging are desired as such welds do not require a second welding pass for filling up the upper bead depressions (UBDs) and characterized with minimum angular distortion. The present paper describes optimization and prediction of angular distortion and weldment characteristics such as upper weld bead depression and lower weld bead bulging of TIG-welded structural steel square butt joints. Full factorial design of experiment was utilized for selecting the combinations of welding process parameter to produce the square butts. A mathematical model was developed to establish the relationship between TIG welding process parameters and responses such as upper bead width, lower bead width, UBD, lower bead height (bulging), weld cross-sectional area, and angular distortions. The optimal welding condition to minimize UBD and lower bead bulging of the TIG butt joints was identified.     

Role of Welding Parameters Using the Flux Cored Arc Welding Process of Low Alloy Steels on Bead Geometry and Mechanical Properties

Welding parameters have direct effects on the bead geometry, microstructure, and mechanical properties of low alloy steels. A series of experiments have been carried out to examine some of these parameters using the flux cored arc welding process (FCAW). In this article, an experimental study was conducted to investigate the influence of welding parameters in FCAW process particularly welding voltage and travel speed on weld bead dimensions. The study also includes the effects of bead overlap and deposition sequence on the parent material and the heat-affected zone (HAZ) properties. It was found that an increase in the welding voltage leads to an increase in the weld bead width, and the increase in the welding traverse speed leads to a decrease in the weld bead width. When studying the bead overlap percentages, it was found that the 50% bead overlap can be considered to be practically a better option than the higher percentages of bead overlap (i.e., 70-90%). The experimental investigation of studying the deposition sequence showed that there were no significant differences in the microstructure, hardness, and the size of the refined HAZ between the two proposed deposition sequences. However, a significant improvement in the microstructure and the size of the refined HAZ, and a reduction in the hardness were achieved after depositing the second welding bead, irrespective of the depositing sequence.     

Prediction and Optimization of Pulsed Current Gas Tungsten Arc Welding Process Parameters to Obtain Sound Weld Pool Geometry in Titanium Alloy Using Lexicographic Method

In this article the weld pool geometry of pulsed current gas tungsten arc (GTA)-welded titanium alloy was analyzed. Increase in use of pulsed current process creates dependancy on the use of mathematical equations to predict the weld pool geometry. Hence, the development of mathematical models using four factors, five levels, central composite design was attempted. The developed models were checked for their adequacy. Lexicographic method was used for optimizing the process parameters of pulsed current GTA welding technique. Optimizing the process parameters has resulted in bringing out strong weld pool geometry, which was later confirmed by conducting confirmation tests.     

Evaluation of the effect of heat input in superduplex stainless steel deposition by the plasma powder process*

Plasma powder surfacing is one of the latest processes for application of coatings, with control of dilution as its main feature. Surfacing with superduplex stainless steels is an interesting option for the construction and repair of equipment for applications in a highly corrosive environment, allowing the desired characteristics to be achieved: corrosion resistance and good mechanical properties. The aim of this work is to assess the ferrite content in the weld metal and the mechanical characteristics via microhardness profiles in surfacing of C-Mn steel pipes with deposition of UNS S32760 by plasma powder surfacing. Welding operations were carried out on pipes with deposition of SDSS, employing three welding heat input levels, varying the welding speed or the welding current. Then the geometry was analysed, the ferrite content in the weld metal was quantified and the microhardness profile was recorded. Variation in welding heat input caused changes in weld bead geometry, with variation in the welding current producing the most significant changes. Increase in heat input caused decrease in ferrite content of the weld metal. Regarding microhardness, only the condition with a higher level of welding current gave sufficiently high levels of microhardness in the weld metal.     

Mathematical Modeling of Weld Bead Geometry, Quality, and Productivity for Stainless Steel Claddings Deposited by FCAW

In recent years, industrial settings are seeing a rise in the use of stainless steel claddings. The anti-corrosive surfaces are made from low cost materials such as carbon steel or low alloy steels. To ensure the final quality of claddings, however, it is important to know how the welding parameters affect the process??s outcome. Beads should be defect free and deposited with the desired geometry, with efficiency, and with a minimal waste of material. The objective of this study then is to analyze how the flux-cored arc welding (FCAW) parameters influence geometry, productivity, and the surface quality of the stainless steel claddings. It examines AISI 1020 carbon steel cladded with 316L stainless steel. Geometry was analyzed in terms of bead width, penetration, reinforcement, and dilution. Productivity was analyzed according to deposition rate and process yield, and surface quality according to surface appearance and slag formation. The FCAW parameters chosen included the wire feed rate, voltage, welding speed, and contact-tip-workpiece distance. To analyze the parameters?? influences, mathematical models were developed based on response surface methodology. The results show that all parameters were significant. The degrees of importance among them varied according to the responses of interest. What also proved to be significant was the interaction between parameters. It was found that the combined effect of two parameters significantly affected a response; even when taken individually, the two might produce little effect. Finally, the development of Pareto frontiers confirmed the existence of conflicts of interest in this process, suggesting the application of multi-objective optimization techniques to the sequence of this study.     

Selection of optimal welding condition for GTA pulse welding in root-pass of V-groove butt joint

In the manufacture of high-quality welds or pipeline, a full-penetration weld has to be made along the weld joint. Therefore, root-pass welding is very important, and its conditions have to be selected carefully. In this study, an experimental method for the selection of optimal welding conditions is proposed for gas tungsten arc (GTA) pulse welding in the root pass which is done along the V-grooved butt-weld joint. This method uses response surface analysis in which the width and height of back bead are chosen as quality variables of the weld. The overall desirability function, which is the combined desirability function for the two quality variables, is used as the objective function to obtain the optimal welding conditions. In our experiments, the target values of back bead width and height are 4 mm and zero, respectively, for a V-grooved butt-weld joint of a 7-mm-thick steel plate. The optimal welding conditions could determine the back bead profile (bead width and height) as 4.012 mm and 0.02 mm. From a series of welding tests, it was revealed that a uniform and full-penetration weld bead can be obtained by adopting the optimal welding conditions determined according to the proposed method.     

CMT工艺及其热输入对Al-Cu合金焊缝成形和气孔的影响

采用四种冷金属过渡焊接工艺(CMT)分别在不同热输入水平下,使用ER2319焊丝进行AA2219-T851高强铝合金的平板堆焊成形,全面分析其焊缝成形和气孔分布特征。结果表明,常规CMT焊缝具有明显指状熔深特征,气孔缺陷严重并呈全焊缝分布状态;CMT-P焊缝母材熔化面积明显增加,气孔数量显著减少且在适当控制热输入时有助于消除气孔;CMT-ADV焊缝也具有指状熔深特征但熔深显著减小;CMT-PADV焊缝具有显著球形熔滴成形特征且熔深最小,两工艺低热输入和对焊丝表面氧化膜的清理作用有助于消除气孔。     

Artificial neural network approach for estimating weld bead width and depth of penetration from infrared thermal image of weld pool

Abstract

In this article an artificial neural network based system to predict weld bead geometry using features derived from the infrared thermal video of a welding process is proposed. The multilayer perceptron and radial basis function networks are used in the prediction model and an online feature selection technique prioritises the features used in the prediction model. The efficacy of the system is demonstrated with a number of welding experiments and using the leave one out cross-validation experiments.     

Prediction of bead geometry in pulsed GMA welding using back propagation neural network

This paper presents the development of a back propagation neural network model for the prediction of weld bead geometry in pulsed gas metal arc welding process. The model is based on experimental data. The thickness of the plate, pulse frequency, wire feed rate, wire feed rate/travel speed ratio, and peak current have been considered as the input parameters and the bead penetration depth and the convexity index of the bead as output parameters to develop the model. The developed model is then compared with experimental results and it is found that the results obtained from neural network model are accurate in predicting the weld bead geometry.     

脉冲PAW快速成形焊缝尺寸的预测模型

介绍了一种基于脉冲等离子焊接快速成形的方法,并采用Taguchi法对单道成形试验进行了合理设计,从而获得了多组焊接工艺参数下的熔宽和余高数据.通过遗传算法（GA）结合BP神经网络的方法建立了等离子焊接快速成形的预测模型,该模型预测了不同焊接成形工艺参数下单道成形的熔宽和余高.结果表明,通过误差分析和线性回归的方法验证了模型具有较高的预测精度和泛化能力,能够合理的预测焊道尺寸,并能推广到多层多道堆积成形尺寸的预测.     

Effects of laser phase transformation hardening parameters on heat input and hardened-bead profile quality of unalloyed titanium

Laser transformation hardening (LTH) of unalloyed titanium of 1.6 mm-thick sheet, nearer to ASTM Grade 3 of chemical composition was investigated using 2 kW CW Nd:YAG laser. The effects of laser power (750-1 250 W), scanning speed (1 000- 3 000 mm/min) and focal point position (from -10 to -30 mm) on the heat input, and hardened-bead geometry (i.e. hardened bead width (HBW), hardened depth (HD) and angle of entry of hardened bead profile with the surface (AEHB)) were investigated using response surface methodology (RSM). The experimental plan is based on Box-Behnken design matrix method. Linear and quadratic polynomial equations for predicting the heat input and the hardened bead geometry were developed. The results indicate that the proposed models predict the responses adequately within the limits of hardening parameters being used. It is suggested that regression equations can be used to find optimum hardening conditions for desired criteria.     

焊接热循环过程中氢陷阱热释放的数值分析

基于焊接热循环过程的特点,分别提出了热循环的升温段和冷却段过程中氢陷阱的热释放的动力学模型,并运用数值分析的方法,对焊接热循环中氢陷阱的热释放过程进行了研究.结果表明,高强度低合金钢的多层多道焊中,前一焊道受后续焊道的热循环作用下,焊道中的氢陷阱存在热释放过程,且弱氢陷阱在热循环的升温段就基本完全被释放出去,而稳定性较...     

Development of torch position control and welding condition control technology for all‐position,multi‐layer GTA welding. Development of fully automatic GTA welding system for pipes (2nd Report)

In pulsed TIG welding, the current varies between two well-defined energy levels in a given frequency, thus being necessary to regulate a set of variables consisting of the peak current, peak time, background current, background time and the welding speed. Yet despite being a widespread technique, in practice, these welding variables are often regulated arbitrarily. This can lead to inefficient use of the pulsed current regarding the end result of the weld and aspects of productivity. This paper aims to present a roadmap developed in order to meet the practical need to establish criteria to assist in the determination of pulsed TIG welding variables, taking as its premise the desired width of the weld bead, overlap between the weld points comprising the weld bead and the welding speed. Finally, one application of this roadmap is presented in bead on plate welding of stainless steel plates with 1.2-mm thickness.     

Optimization of back bead geometry in the PMAG-TIG twin arc hybrid root welding process using grey based Taguchi method

This study investigated multi-response optimization of the pulse metal active gas-tungsten inert gas( PMAG-TIG) twin arc hybrid root welding process for an optimal parametric combination to yield favorable back bead geometry of welded joints using grey relational analysis and Taguchi method.Eighteen experimental runs based on an orthogonal array following the Taguchi method were performed to derive objective functions to be optimized within the experimental domain.The objective functions were selected in relation to parameters of PMAG-TIG twin arc root welding back bead geometry: back bead width to root reinforcement ratio and deposited metal height.The Taguchi approach was followed by grey relational analysis to solve the multi-response optimization problem.The significance of factors on overall quality characteristics of the weld joint was also evaluated quantitatively using analysis of variance.Optimal results were verified through additional experiments,and showed to feasibility of applying grey relation analysis in combination with Taguchi technique for continuous improvement of product quality in the manufacturing industry.